THE ORIGIN OF SPECIES. 53 



duced by breeding with a view to one cliar'acteiistic 

 often differs all round from the parent stock. 



Theory of Evolution. To trace the analogy be- 

 tween the work of the gardener or the cattle-breeder 

 and the work of nature, and to interpret nature in the 

 light of this analogy, was the great task of a great 

 and patient mind. One principle is seen underlying 

 that analogy, the principle, namely, that the existing 

 forms of life, in their infinite variety, have been pro- 

 duced, and are still in course of being produced, by 

 the infinite modifications of outward circumstances, 

 from other and different forms. One conclusion is in- 

 evitably suggested by this, namely, that all forms of 

 life have in the distant past diverged gradually from 

 a common source. 



Some glimmering of these ideas had found its way 

 into the minds of previous writers ; but it was Darwin's 

 wide knowledge of the facts of nature which gave them 

 the clear intelligible form and the tremendous evi- 

 dential force that ensm-ed their reception by open and 

 candid minds. They were in harmony, too, with the 

 aspirations of the modern world ; they seemed the 

 very embodiment of the spirit of the age. In the light 

 given by these ideas, not only were existing systems 

 of natural history revolutionized, bat also existing 

 modes of thought. Never was novel truth more 

 gladly welcomed by an eager world, or more readily 

 incorporated into the intellectual life of the day. And 

 never, since the time of Galileo, was a novel exposition 

 of scientific facts so virulently attacked by those who 



